US10277147B2 - Triboelectric nanogenerators based on chemically treated cellulose - Google Patents
Triboelectric nanogenerators based on chemically treated cellulose Download PDFInfo
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- US10277147B2 US10277147B2 US15/178,285 US201615178285A US10277147B2 US 10277147 B2 US10277147 B2 US 10277147B2 US 201615178285 A US201615178285 A US 201615178285A US 10277147 B2 US10277147 B2 US 10277147B2
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
- H02N1/00—Electrostatic generators or motors using a solid moving electrostatic charge carrier
- H02N1/04—Friction generators
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
- B29C43/02—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/04—Coating on selected surface areas, e.g. using masks
- C23C16/045—Coating cavities or hollow spaces, e.g. interior of tubes; Infiltration of porous substrates
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
- C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
- C23C16/455—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
- C23C16/45523—Pulsed gas flow or change of composition over time
- C23C16/45525—Atomic layer deposition [ALD]
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
- C23C16/455—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
- C23C16/45523—Pulsed gas flow or change of composition over time
- C23C16/45525—Atomic layer deposition [ALD]
- C23C16/45555—Atomic layer deposition [ALD] applied in non-semiconductor technology
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2001/00—Use of cellulose, modified cellulose or cellulose derivatives, e.g. viscose, as moulding material
- B29K2001/08—Cellulose derivatives
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
- B29K2995/0018—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds having particular optical properties, e.g. fluorescent or phosphorescent
- B29K2995/0026—Transparent
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B29L2031/00—Other particular articles
- B29L2031/34—Electrical apparatus, e.g. sparking plugs or parts thereof
Definitions
- TENGs are advantageous in terms of their high efficiencies, high power densities, light weight, low cost, and manufacturability.
- a TENG functions under the coupling effects of contact electrification and electrostatic induction. The working principle requires two dissimilar surfaces to be oppositely charged upon contact.
- the common positive materials in TENGs are polyamides, metals, indium tin oxide (ITO), and zinc oxide.
- Common negative materials include fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), and polyethylene terephthalate (PET).
- FEP fluorinated ethylene propylene
- PTFE polytetrafluoroethylene
- PVDF polyvinylidene fluoride
- PDMS polydimethylsiloxane
- PET polyethylene terephthalate
- TENGs and methods for fabricating the TENGs are provided. Also provided are methods for using the TENGs to harvest mechanical energy and convert it into electric energy.
- a triboelectric nanogenerator comprises: a first electrode comprising a positive active layer comprising cellulose, the positive active layer having a front surface with a positive surface charge and an oppositely facing back surface; a second electrode comprising a negative active layer comprising cellulose, the negative active layer having a front surface with a negative surface charge and an oppositely facing back surface; optionally, a third electrode comprising a third active layer that is either a positive active layer comprising cellulose or a negative active layer comprising cellulose, the third active layer having a front surface with a positive surface charge, if it is a positive active layer, or a negative surface change, if it is a negative active layer, and an oppositely facing back surface; wherein the positive active layer, the negative active layer, and, if present, the third active layer are dielectric layers; a first electrically conducting contact layer on the back surface of one of the positive active layer, the negative active layer, or, if present, the third active layer; a second electrically conducting contact layer on the
- each of the positive active layer, the negative active layer, and, if present, the third active layer is disposed opposite and facing the front surface of at least one other of the positive active layer, the negative active layer, and, if present, the third active layer.
- the positive active layer, the negative active layer, and, if present, the third active layer are configured to be moved with respect to one another in a periodic manner that generates a periodically varying electric potential difference between the first electrically conducting contact layer and the second electrically conducting contact layer.
- the cellulose of at least one of the positive active layer, the negative active layer, and, if present, the third active layer comprises a chemical functional group that provides the negative and positive active layers with different electron affinities.
- a triboelectric nanogenerator may comprise: a positive active layer comprising cellulose, the positive active layer having a front surface and an oppositely facing back surface; a first electrically conducting contact layer on the back surface of the positive active layer; a negative active layer comprising cellulose, the negative active layer having a front surface and a back surface, wherein the negative active layer has a higher electron affinity than the positive active layer; a second electrically conducting contact layer on the back surface of the negative active layer; and an external load connected across the first and second contact layers, such that the first and second contact layers are in electrical communication through the external load.
- the cellulose of at least one of the positive and negative active layers comprises a chemical functional group that provides the negative and positive active layers with different electron affinities.
- the front surface of the positive active layer is disposed opposite and facing the front surface of the negative active layer and the positive and negative active layers are configured to be moved with respect to one another in a periodic manner that generates a periodically varying electric potential difference between the first contact layer and the second contact layer.
- One embodiment of a method of converting mechanical energy into an electrical current using a triboelectric nanogenerator as described herein includes the steps of: (a) bringing the front surface of the positive active layer into contact with the front surface of the negative active layer, wherein electrons from the positive active layer are injected into the negative active layer, such that a positive surface charge accumulates on the positive active layer and a negative surface charge accumulates on the negative active layer; (b) applying a force to at least one of the positive and negative active layers that moves the front surface of the positive active layer with respect to the front surface of the negative active layer in a manner that generates a potential difference between the first and second contact layers, wherein electrons are transferred from either the first or the second contact layer, through the external load, and to the other contact layer until the potentials of the first and second contact layers become equal; (c) applying a reverse force to at least one of the positive and negative active layers that moves the front surface of the positive active layer with respect to the front surface of the negative active layer in a manner that regenerates
- One embodiment of a method of making a triboelectric nanogenerator comprises the step of forming a first electrode by: forming a first active layer comprising cellulose on a substrate, the first active layer having a front surface and an oppositely facing back surface; functionalizing the cellulose of the first active layer with one or more chemical functional groups that change the electron affinity of the cellulose relative to that of unfunctionalized cellulose; and forming a first contact layer on the back surface of the first active layer.
- the method further comprising the step of forming a second electrode by: forming a second active layer comprising cellulose on a substrate, the second active layer having a front surface and an oppositely facing back surface, wherein the cellulose of the second active layer has a different electron affinity than the cellulose of the first active layer; and forming a second contact layer on the back surface of the second active layer.
- the method still further comprising the step of arranging the first active layer and the second active layer such that the front surface of the first active layer is disposed opposite and facing the front surface of the second active layer and the first and second active layers are configured to be moved with respect to one another in a periodic manner that generates a periodically varying electric potential difference between the first contact layer and the second contact layer.
- FIG. 1A Schematic diagram showing a cyclic compressive force being applied to a vertical contact mode TENG.
- FIG. 1B Schematic diagram showing a cyclic sliding force being applied to a lateral sliding mode TENG.
- FIG. 1C Schematic diagram showing a lateral force being applied to the mobile triboelectric layer of a free-standing triboelectric layer mode TENG.
- FIG. 2 Chemical structures of amine-, ethyl-, sulfate-, and acetate-functionalized cellulose, as well as unfunctionalized cellulose and nitro- and fluoro-functionalized cellulose.
- FIG. 3 Atomic force microscopy (AFM) topography image of a CNF film surface.
- FIG. 4A The open circuit voltage (Voc) (c) measured from CNF film-based TENGs built with different pairs of active materials.
- FIG. 4B The short circuit current (Isc) measured from CNF film-based TENGs built with different pairs of active materials.
- FIG. 5A Measured voltage output (dots), calculated voltage output (circles), and measured triboelectric charge transfer (diamonds) as a function of active CNF film area (Aeff).
- FIG. 5B Calculated RC discharging curves for TENGs with different Aeff.
- FIG. 5C Voltage and current output of a TENG as a function of the load resistance.
- FIG. 5D Calculated output power of a TENG as a function of the load resistance.
- FIG. 6A Voltage measured across a 10 ⁇ F capacitor when it was charged by a TENG under different frequencies of mechanical impacts.
- FIG. 6B The energy stored in a capacitor calculated from the capacitor charging curves as a function of mechanical impact frequency. The TENG was successfully used as a direct current power source to light up 150 green LEDs connected in series.
- FIG. 7A Open-circuit voltage (Voc) output of a triboelectric fiberboard when a person of normal weight stepped on repeatedly for ⁇ 30 times. Inset is the Voc during one stepping.
- FIG. 7B Short-circuit current (Isc) output of the triboelectric fiberboard when a person of normal weight stepped on repeatedly for ⁇ 30 times.
- FIG. 8 Schematic diagram showing the initial state and the equilibrium state of a CNF-based TENG in the process of charge transfer.
- the TENG as a capacitor is identical to three capacitors connected in series: CNF film, air gap, and FEP film. To the left of the final equilibrium state is the identical circuit of the TENG system during voltage measurement.
- FIG. 9A Triboelectric output from a cellulose pair composed of two pristine (unfunctionalized) cellulose films.
- FIG. 9B Triboelectric output from a cellulose pair composed of a nitro group-containing and a pristine cellulose film.
- FIG. 9C Triboelectric output from a cellulose pair composed of a methyl group-containing and a pristine cellulose film.
- FIG. 9D Triboelectric output from a cellulose pair composed of an amine group-containing and a pristine cellulose film.
- FIG. 9E Triboelectric output from a cellulose pair composed of: a methyl group-containing and a nitro group-containing cellulose film.
- FIG. 9F Triboelectric output from a cellulose pair composed of: a methyl group-containing and a nitro group-containing cellulose film.
- FIG. 9G Triboelectric output from a cellulose pair composed of a methyl group-containing and an amine group-containing cellulose film.
- TENGs and methods for fabricating the TENGs are provided. Also provided are methods for using the TENGs to harvest mechanical energy and convert it into electric energy.
- one or both of the triboelectrically active layers comprises a cellulose that has been chemically treated to alter its electron affinity.
- TENGs in which both triboelectrically active layers comprise a cellulose material can be fabricated. This is advantageous because cellulose is a readily available, inexpensive, and biodegradable material derived from a renewable resource.
- the nanogenerators can be used to convert mechanical energy into electric current for a variety of applications.
- the TENGs can be used to drive small electronics, charge batteries and capacitors, and drive chemical reactions. Because they can have small, flexible, and light weight designs, the TENGs are well suited for use in portable and wearable electronic devices.
- the TENGs include two electrodes, each of which comprises an active layer comprising cellulose and a contact layer, which is an electrically conducting layer in electrical communication with the active layer.
- the cellulose in each of the two active layers has a different electron affinity, which results in a transfer of charges when the active layers come into contact.
- the two electrodes are configured to be moved with respect to one another, after they make initial contact, in a manner that generates a periodically varying electric potential difference between their contact layers.
- the motion that generates the periodic potential difference can be, for example, a vertical motion that brings the two active layers into and out of contact (as in a vertical contact mode TENG) or a sliding motion that slides the two active layers into and out of contact (as in a sliding mode TENG).
- the periodically varying potential difference can be used to drive an alternating electric current through that load.
- the active layers are triboelectrically active and electrically insulating.
- the “positive” active layer is so called because it has a lower electron affinity than the “negative” active layer and, therefore, acquires a positive surface charge via electron transfer when the two active layers are brought into contact.
- the “negative” active layer is so called because it has a higher electron affinity than the “positive” active layer and, therefore, acquires a negative surface charge via electron transfer when the two active layers come into contact.
- the cellulose of the positive action layer, the negative active layer, or both is treated so that it comprises chemical functional groups that alter the electron affinity of the cellulose.
- These functional groups may be incorporated into the cellulose by, for example, incorporating molecules comprising the functional groups into the cellulose of the active layer without chemical bonds, or they may be incorporated by reacting the cellulose with molecules comprising the functional groups to form chemically bonded chemical functionalities on the cellulose.
- the chemical functional groups can be incorporated deep enough into the cellulose of the active layers to change the bulk electric properties of the active layers.
- the resulting layer of chemically modified cellulose can be distinguished from layers of cellulose that are only modified at their outer surfaces using such methods as plasma surface modification.
- the optimal thickness of the active layers may vary, the active layers typically have thicknesses in the range from about 10 ⁇ m to a few mm. This includes active layers having a thickness in the range from about 50 ⁇ m to about 1 mm.
- the chemical functional groups incorporated into the active layers can be electron donating groups or electron withdrawing groups.
- electron donating groups include amine groups, methyl groups, ethyl groups, sulfate groups, acetate groups, and combinations thereof.
- the structures of amine-, ethyl-, sulfate-, and acetate-functionalized cellulose, as well as unfunctionalized cellulose are shown in FIG. 2 , panels (a) through (e).
- Examples of electron withdrawing groups include nitro groups, chlorine groups, fluorine groups, and combinations thereof.
- the structures of nitro- and fluoro-functionalized cellulose are shown in FIG. 2 , panels (f) and (g).
- the chemical functional groups listed as electron donating groups above can also be to functionalize both the positive and negative active layers, provided that the positive active layer is functionalized with a functional group that is more strongly electron donating.
- the chemical functional groups listed as electron withdrawing groups above can be used to functionalize both the positive and negative active layers, provided that the negative active layer is functionalized with a functional group that is more strongly electron withdrawing.
- methyl groups can be used to functionalize the positive active layer or the negative active layer.
- the positive active layer is functionalized with an electron donating group and the negative active layer is functionalized with an electron withdrawing group.
- TENGs having a larger difference between the electron affinity of their positive active layer and their negative active layer can provide higher power densities. Therefore, for some applications it may be advantageous to treat the cellulose of both the positive and negative active layers to maximize this difference.
- the cellulose of the positive active layer can be chemically functionalized with at least one of amine groups, ethyl groups, or methyl groups and the cellulose of the negative active layer can be functionalized with at least of chlorine groups or fluorine groups.
- the cellulose of the active layers can be characterized by its surface charge density.
- surface charge density can be measured after contact with a gold (Au) surface, as discussed in Example 2.
- Some embodiments of the positive active layer comprising a chemically treated cellulose have a surface charge density of at least +1 pC/cm 2 after contact with an Au surface. This includes embodiments of the positive active layer that have a surface charge density of at least +1.2 pC/cm 2 after contact with an Au surface and further includes embodiments of the positive active layer that have a surface charge density of at least +1.4 pC/cm 2 after contact with an Au surface.
- Some embodiments of the negative active layer comprising a chemically treated cellulose have a surface charge density of ⁇ 1.5 pC/cm 2 or lower after contact with an Au surface. This includes embodiments of the negative active layer that have a surface charge density of ⁇ 2 pC/cm 2 or lower after contact with an Au surface and further includes embodiments of the negative active layer that have a surface charge density of ⁇ 2.5 pC/cm 2 or lower after contact with an Au surface.
- the cellulose in the positive and/or negative active layer is present as one component in a lignocellulosic material
- a lignocellulosic material refers to a plant-based material comprising the cellulose, along with hemicelluloses and lignin.
- the lignocellulosic material may be a natural material, such as wood, that has undergone some minimal mechanical processing, but otherwise retains its natural wood composition.
- Wood chips which include shavings and sawdust, and materials comprising wood chips and, optionally, a binder and other additives, are examples of materials comprising natural lignocellulosic materials.
- the lignocellulosic material may have undergone chemical processing to selectively extract and purify its cellulose component.
- examples of such materials include fiberboards, including recycled fiberboards.
- Fiberboards comprise plant-extracted cellulose fibers, which may be obtained from wood and other plant matter by, for example, bleaching and pulping.
- Highly purified cellulose nanofibrils (CNFs) are another example of a processed, plant extracted material that may be used as the cellulose of the active layers in the TENGs.
- CNFs comprise both amorphous and crystalline cellulosic domains and are characterized by nanoscale widths and microscale lengths.
- CNFs are sometimes referred to as nanocellulose fibrils (NFC) or nanofibers.
- NFC nanocellulose fibrils
- CNFs have high surface areas, can be functionalized with a variety of chemical groups, and can be formed into optically transparent films.
- optically transparent means transparent in the visible region of the electromagnetic spectrum.
- the first and second contact layers are electrically conducting layers that are in electrical communication through one or more external loads, as discussed in greater detail below. They comprise an electrically conducting material, which may be a metal, such as gold, or a conducting oxide, such as indium tin oxide (ITO), or a carbon-base material, such as graphite.
- the contacts are typically, but not necessarily, deposited as thin films on the back surfaces of their respective active layers.
- the contact layers can be disposed on a support substrate, such that at least a portion of the contact layer is sandwiched between the support substrate and the active layer.
- the support substrates are desirably comprised of thin, flexible materials, such as polymers. Examples of suitable polymer supports include polyethylene naphthalate, polyethylene terephthalate (PET), polyimide, or poly-ether-ether-ketone.
- FIG. 1A depicts one embodiment of a vertical contact mode TENG that includes: (a) a positive active layer 102 comprising cellulose, the positive active layer having a front surface 101 and an oppositely facing back surface 103 ; (b) a first contact layer 104 on back surface 103 of positive active layer 102 (together, layers 102 and 104 provide a first electrode); (c) a negative active layer 106 comprising cellulose, the negative active layer having a front surface 105 and a back surface 107 , wherein negative active layer 106 has a higher electron affinity than positive active layer 102 ; and (d) a second contact layer 108 on back surface 107 of negative active layer 106 (together layers 106 and 108 provide a second electrode).
- An external load 110 is connected across first and second contact layers 102 , 106 , such that first and second contact layers 104 , 108 are in electrical communication through external load 110 .
- Front surface 101 of positive active layer 102 is disposed opposite and facing front surface 105 of negative active layer 106 , such that the front surface of the positive active layer and the front surface of the negative active layer are separated by a gap 112 when the triboelectric nanogenerator is in an uncompressed state.
- the cellulose of at least one of the positive and negative active layers comprises a chemical functional group that provides the negative and positive active layers with different electron affinities.
- the front surfaces of the positive and negative active layers face each other, but are separated by a gap when the TENG is in an uncompressed state.
- the TENG is configured such that the positive and negative active layers can go from the uncompressed state, to a compressed state in which their front surfaces are in contact, and back to an uncompressed state in a series of compression cycles.
- the positive and negative active layers may be connected to one another via a flexible, elastic connector.
- one or both of the active layers may serve as, or be mounted to, a moveable platform that brings the two active layers into contact when a compressive force is applied.
- FIG. 1A The operation of a vertical contact mode TENG is illustrated schematically in FIG. 1A .
- the TENG is in an uncompressed state (panel (a)) in which the positive active layer and the negative active layer are not in contact and a potential difference has not yet been generated between the first and second contact layers.
- panel (a) the positive active layer is disposed above the negative active layer in FIGS. 1A-1C , these positions can be reversed.
- a compressive force is then repeatedly applied to one or both of the positive and negative active layers and then released.
- the initial application of the compressive force brings the front surfaces of the positive and negative active layers into contact, as shown in panel (b). Due to their differing triboelectric properties, electrons from the positive active layer are injected into to negative active layer.
- the release/compress cycle can be repeated by cycling repeatedly through the steps illustrated in panels (b) through (e) in FIG. 1A .
- the compressive force can occur at regular intervals or irregular intervals and may be generated by a wide variety of sources, including a person walking, running, or breathing, or by the vibrations of an engine or the rotation of a tire.
- the TENGs can also be operated in a sliding mode, including a lateral sliding mode and a rotational sliding mode.
- a sliding mode TENG a periodic change in the contact area between the front surfaces of the positive and negative active layers results in a periodic lateral separation of the charge carriers. This creates a periodic potential difference between the two active layers that can be used to drive an external load.
- FIG. 1B The operation of a lateral sliding mode TENG is illustrated in FIG. 1B .
- the components of the TENG are the same as those for the vertical contact mode TENG of FIG. 1A .
- the positive and negative active layers are configured such that their front surfaces are able to slide over one another, such that the active layers can go from a state of high contact area to a state of low (or no) contact area and then back to a state of high contact area in a series of sliding cycles.
- the positive and negative active layers may be connected to one another via a flexible, elastic connector.
- one or both of the active layers may serve as, or be mounted to, a moveable platform that laterally slides the front surface of one of the active layers with respect to the front surface of the other active layer.
- the first and second contact layers of the lateral sliding mode TENG are connected across an external load, which is powered by the TENG when the TENG is in operation.
- first contact layer 104 is in electrical communication with second contact layer 108 through external load 110 (depicted here as an LED) (panel (a)).
- external load 110 (depicted here as an LED) (panel (a)).
- the contact area of the front surface 101 of positive active layer 102 and the front surface 105 of negative active layer 106 is maximized. Due to their differing triboelectric properties, electrons from the positive active layer are injected into the negative active layer. This results in the accumulation of a positive surface charge on the positive active layer and a negative surface charge on the negative active layer. As a result, electrons flow from the second contact layer, through the external load, and into the first contact layer.
- the external load is illustrated by an LED, which is lit by the current.
- a sliding force is applied to one or both of the active layers, positive active layer 102 slides outward with respect to negative active layer 106 .
- the resulting decrease in the contact area between the two active layers results in an in-plane charge separation that creates a potential difference between the first and second contact layers (panel (c)).
- electrons flow from the first contact layer, through the LED and into the second contact layer, lighting up the LED.
- the sliding process continues until contact area between the front surfaces of the positive and negative active layers is eliminated, at which point the potential difference between the first and second contact layer disappears and the current stops flowing (panel (d)).
- the sliding force can occur at regular intervals or irregular intervals and may be generated by a wide variety of sources, including a person walking, running, or breathing, or by the vibrations of an engine or the rotation of a tire.
- the TENGs can also be operated in a freestanding triboelectric-layer mode.
- a periodic change in the position of the active layer of a mobile electrode relative to the active layers in a pair of stationary electrodes creates a periodic potential difference between the two stationary electrodes that can be used to drive an external load.
- the freestanding triboelectric-layer mode TENG comprises a mobile electrode 111 comprising a positive active layer 102 comprising a layer of cellulose, a first stationary electrode 113 , and a second stationary electrode 115 (i.e., a third electrode).
- Each of the first and second stationary electrodes has the same construction as the second electrode in FIG. 1A and comprises a negative active layer 106 comprising cellulose and a second contact layer 108 on the back surface of negative active layer 106 .
- the positive active layer 102 of mobile electrode 111 is disposed directly over the negative active layer 106 of the first stationary electrode 113 .
- FIG. 1C The operation of a lateral sliding mode TENG is illustrated in FIG. 1C .
- the freestanding triboelectric-layer mode TENG comprises a mobile electrode 111 comprising a positive active layer 102 comprising a layer of cellulose, a first stationary electrode 113 , and a second stationary electrode 115 (i.e., a third electrode).
- the cellulose in positive active layer 102 of mobile electrode 111 and the cellulose in negative active layer 106 of stationary electrode 113 have undergone a charge transfer, such that the former has a positive surface charge and the latter has a negative surface charge.
- the negative surface charge on the front surface of negative active layer 106 induces a positive charge on its back surface which, in turn, induces a negative charge in underlying contact layer 108 .
- the sliding force that causes the mobile electrode to shift back-and-forth between the stationary electrodes can occur at regular intervals or irregular intervals and may be generated by a wide variety of sources, including a person walking, running, or breathing, or by the vibrations of an engine or the rotation of a tire.
- the cyclic signal output of the TENGs is an alternating current (AC). However, it can be converted into a direct current (DC) by a rectification circuit.
- the load may comprise, for example, a battery, a capacitor, a sensor, such as a motion or vibration sensor, a light-emitting device, such as a light-emitting diode (LED), or a combination of one or more thereof.
- the TENGs can be made by making a first electrode by forming a first active layer comprising cellulose, functionalizing the cellulose of the first active layer with one or more chemical functional groups that change the electron affinity of the cellulose relative to that of unfunctionalized cellulose, and forming a first contact layer on the back surface of the first active layer.
- the functionalization of the cellulose can take place prior to, or after, the active layer is formed.
- a second electrode can be made by forming a second active layer comprising cellulose and forming a second contact layer onto the back surface of the second active layer.
- the cellulose of the second active layer is either unfunctionalized or differently functionalized, such that it has a different electron affinity than the cellulose of the first active layer.
- the first and second active layers are then configured (i.e., designed) such that the front surface of the first active layer is disposed opposite and facing the front surface of the second active layer.
- the cellulose of the second active layer is also functionalized with one or more chemical functional groups that change the electron affinity of the cellulose relative to that of unfunctionalized cellulose.
- the chemical functional groups incorporated into the first active layer impart the cellulose with a lower electron affinity, so that the first active layer serves as a positive active layer and the chemical functional groups incorporated into the second active layer impart the cellulose with a higher electron affinity, so that the second active layer serves as a negative active layer.
- the cellulose can be functionalized, for example, by exposing the cellulose to a vapor comprising precursor molecules that include the chemical functional groups, wherein the precursor molecules infiltrate the first active layer and react with the cellulose to form the chemical functional groups in the cellulose.
- a vapor comprising precursor molecules that include the chemical functional groups This method is illustrated in Example 1.
- the doping of the active layer can extend well into the layer.
- the chemical functional groups extend into the layer to a depth of at least 1 ⁇ m, starting from the front surface and any other exposed surface(s).
- the corresponding percentage of the active layer that is chemically functionalized at these depths will depend on the thickness of the active layer. However, in some embodiments of the active layers the chemical functional groups extend through at least 1% of the thickness of the active layer, starting from its front surface and any other exposed surface(s).
- the active layers in which the chemical functional groups extend through at least 2% of the thickness of the active layer, through at least 5% of the thickness of the active layer, through at least 20% of the thickness of the active layer, and through at least 50% of the thickness of the active layer, starting from its front surface and any other exposed surface(s).
- the active layers comprise the chemical functional groups all the way through their thickness.
- the precursor molecules can be organic molecules or inorganic molecules comprising one or more chemical functional groups, including those discussed above, that are capable of altering the electron affinity of the cellulose.
- the precursor molecules react with —OH groups on the cellulose to form chemical (e.g., covalent) bonds between the cellulose and the chemical functional groups.
- the cellulose may be exposed to water vapor before or at the same time as it is exposed to the precursor molecules, in order to increase the density of reactive —OH groups on the cellulose.
- suitable precursor molecules for functionalizing cellulose with chlorine groups include TiCl 4 , titanium isoporpoxide (TTIP), vanadium tetrachloride (VOCl 3 ), and vanadium oxytriisopropoxide (VTIP).
- suitable precursor molecules for functionalizing cellulose with methyl groups include trimethyl aluminum (TMA), tetrakis(ethylmethylamino)hafnium (Hf(NEtMe) 4 ), tetrakis(dimethylamino) hafnium (HRNMe 2 ) 4 ), and (dimethylamido)zirconium (Zr(NMe 2 ) 4 ).
- TMA trimethyl aluminum
- Hf(NEtMe) 4 tetrakis(ethylmethylamino)hafnium
- HRNMe 2 ) 4 tetrakis(dimethylamino) hafnium
- Zr(NMe 2 ) 4 examples include diethylzinc (DEZ).
- suitable precursor molecules for functionalizing cellulose with fluoro groups include NH 4 F; hexafluoroacetylacetonate (HFAC)+ozone; anhydrous HF gas; TiF 4 ; and TaF 5 .
- suitable precursor molecules for functionalizing cellulose with amino groups include bis(tert-butylamino)silane (BTBAS).
- suitable precursor molecules for functionalizing cellulose with nitro groups include nitrate-containing precursors: Ti(NO 3 ) 2 , Ni(NO 3 ) 2 , Co(NO 3 ) 2 , Cu(NO 3 ) 2 .
- the cellulose can be functionalized in solution, prior to the formation of the active layer. As illustrated in Example 2, this can be done by forming an aqueous or non-aqueous solution comprising cellulose-containing fibers and chemical reactants that comprise the chemical functional groups and reacting the chemical reactants and the cellulose-containing fibers to provide chemical functional groups covalently bonded to the cellulose-containing fibers. (The step of reacting the chemical reactants and the cellulose-containing fibers can be merely allowing them to react under the conditions of the solution.) Functionalizing the cellulose prior to assembling it into an active layer has the advantage that the resulting active layer will comprise the functional groups throughout its thickness.
- the cellulose-containing fibers can be fibers of a lignocellulosic material or fibers extracted and purified from a lignocellulosic material, such as recycled fiberboard fibers.
- CNF film started with the manufacturing of a CNF hydrogel, a process where wood pulp was oxidized and then mechanically homogenized according to Saito's method to achieve water dispersion of cellulose nanofibrils.
- Saito's method See, T. Saito, M. Hirota, N. Tamura, S. Kimura, H. Fukuzumi, L. Heux, A. Isogai, Biomacromolecules 2009, 10, 1992.
- the CNF hydrogel was then filtered and dried under pressure to obtain transparent and flexible CNF thin films (detailed fabrication procedures are included in the method section).
- the thickness of the CNF films was controlled in the range of 70 ⁇ 320 ⁇ m by varying the amount of CNF hydrogel.
- the as-prepared CNF films exhibited a fairly smooth surface without any observable pin holes under low-magnification scanning electron microscope.
- the fibrous feature could be clearly observed by AFM topography scan.
- a typical fiber had a diameter of 230 nm.
- the maximum height difference was approximately 300 nm, suggesting the surface roughness was ⁇ 300 nm.
- the as-prepared film also showed excellent transparency and flexibility. The film can be bent to a great degree and returned to its original shape after releasing it without showing any marks.
- the CNF film was used as the positive active layer and paired with an FEP film as a negative active layer to assemble a TENG.
- FEP was chosen due to its very negative position on the triboelectric series (i.e. far from cellulose).
- the TENG device was built with an identical size (1 cm ⁇ 1 cm) of both CNF and FEP films, each of its own flexible ITO/PET substrate, where ITO was the conducting electrode (i.e., contact layer) and PET was a support for the structure. The distance between the two ITO electrodes was fixed to be 1 mm for all experiments in this study.
- the schematic design is shown in FIGS. 1A-1C . A digital photo showed good transparency of the TENG device.
- CNF films were treated by TiCl 4 exposures, which could introduce electron-giving —Cl groups into the film and make the CNF film more positive in the triboelectric series.
- the TiCl 4 -treated CNF films were used to replace FEP and assembled together with pristine CNF films to fabricate all-CNF-based TENG devices.
- FIG. 4A and FIG. 4B show typical open-circuit voltage (V oc ) and short circuit current (I sc ) output signals measured from the three types of CNF-based TENGs.
- V oc open-circuit voltage
- I sc short circuit current
- TENGs made of typical synthetic polymer pairs such as Kapton-PET and PTFE-polyamide.
- the TENG device built with TiCl 4 -treated CNF films yielded ⁇ 3.5 V average V oc and ⁇ 0.35 ⁇ A average peak I sc ; whereas the outputs from two identical pristine CNF films only reached ⁇ 0.1V of average peak V oc and ⁇ 0.1 ⁇ A of average peak I sc .
- V oc An interesting surface area-related V oc variation was observed when TENGs were made and tested from CNF/FEP films of five different surface areas in the range from 1 cm 2 to 40 cm 2 . In this case, all TENGs had identical electrode spacing of 1 mm. As shown in FIG. 5A , V oc increased monotonically with the increasing of the active area. Testing of the I sc showed the same trend. The maximum V oc and I sc were 32.8 V and 35 ⁇ A, corresponding to 40 cm 2 surface area. However, the principle of TENG describes that the surface charge (Q 0 ) is directly proportional to effective surface area (A eff ) and the ratio between them (Q 0 /A eff ) remains constant for a given TENG. This relationship tells us that V oc should be a constant as a function of A eff following the equation:
- FIG. 5C shows the dependence of the peak V oc and I sc as a function of external load resistance measured from a TENG with a CNF film of 70 ⁇ m thickness and 40 cm 2 surface areas. Same as other TENGs, the V oc monotonically increased with the rising of the load resistance, while the I sc showed an opposite trend, as a result of ohmic loss. Corresponding power output was calculated from the product of V o , and I sc and was plotted in FIG. 5D . The optimal power point was obtained at ⁇ 1 M ⁇ with a peak value of 0.56 mW. It should be noted that the power value presented here is the instantaneous peak power, corresponding to the short and sharp voltage and current peaks. Analyzing the amount of electrical energy produced would be a more practical approach to evaluate its applicant potential.
- the CNF TENG was used to charge capacitors, so as to explore its potential as a continuous direct current (DC) energy supply.
- the experiments were conducted with the TENG connected to the capacitor through a rectification circuit, which converted the alternative current (AC)-type electric output into one direction.
- AC alternative current
- the voltage across the capacitor was measured every 5 seconds for a total of 110 seconds.
- Typical voltage raising profiles across a 10 ⁇ F capacitor are shown in FIG. 6A .
- a saturation charging curve was obtained after ⁇ 40 s operation, which is typical for resistor-capacitor (RC) charging.
- the charging of larger capacitors e.g.
- the feasibility of the TENG as a power source for LEDs at this lowest frequency was tested.
- the TENG was able to light up 150 green LEDs connected in series, proving its capability as a practical DC power source.
- CNF hydrogel was prepared from wood pulp by tetramethylpiperidine-1-oxy (TEMPO)-mediated oxidation and subsequent mechanical homogenization following the method from Saito et al. (See, T. Saito, M. Hirota, N. Tamura, S. Kimura, H. Fukuzumi, L. Heux, A. Isogai, Biomacromolecules 2009, 10, 1992.)
- TEMPO tetramethylpiperidine-1-oxy
- bleached kraft eucalyptus pulps were oxidized in a mixture of TEMPO, sodium hypochlorite (NaClO), and sodium chlorite (NaClO 2 ) under pH 6.8. The oxidation was carried out at 60° C.
- Oxidized pulps were thoroughly washed in distilled water and refined in a disk refiner to break apart the residual fiber bundles. The refined fibers were then separated by centrifuge to remove the supernatant fraction, and concentrated to 1 wt. % using ultrafiltration. Finally, this suspension was subjected to high pressure mechanical homogenization by passing through a series of 200- and 87- ⁇ m chambers on a microfluidizer three times (M-110EH-30 Microfluidizer, Microfluidics, Newton, Mass., USA). The resulting mixture of nanofibrils and water formed a transparent, stable aqueous colloid system (with a cellulose solid weight of 1%), i.e., CNF hydrogel.
- the as-processed CNF hydrogel was diluted with deionized (DI) water and then filtered under approximately 0.55 MPa air pressure in a filtration system (Millipore Corporation, USA).
- DI deionized
- a filtration system Millipore Corporation, USA.
- water within the slurry passed through a polytetrafluoroethylene membrane (0.1 ⁇ m pore sizes), leaving the CNF filter cake.
- the CNF cake was sandwiched between layers of waxy coated paper, filter paper, and caul plates for room temperature drying followed by 65° C. oven drying. During drying, pressure was applied on top by weights to prevent warping and wrinkling. Consequently, the flat, transparent and flexible CNF film was obtained.
- the TENGs used in demonstrating the design and performance of CNF TENGs were fabricated as follows: a pure CNF film with a size of 1 cm ⁇ 1 cm was attached to the center of an indium tin oxide/polyethylene terephthalate (ITO/PET) substrate (2 cm ⁇ 5 cm), which was considered as the top electrode.
- the bottom electrode was composed of another polymer film with the same size and location on the other ITO/PET substrate.
- the bottom polymer film can be fluorinated ethylene propylene (FEP), TiCl 4 treated CNF, or pristine CNF.
- FEP fluorinated ethylene propylene
- TiCl 4 treated CNF was obtained by 30 cycles of TiCl 4 vapor exposure in an atomic layer deposition (ALD) system.
- Each cycle of TiCl 4 exposure lasted 5 seconds and was separated from its subsequent TiCl 4 exposure by 60 seconds of N 2 purging.
- the two electrodes were 1 mm separated using spacers, and connected to the external circuit through copper tapes.
- the thickness of the bottom CNF was 320 ⁇ m, while the thickness of the FEP, top CNF and TiCl 4 coated CNF were all 60 ⁇ m.
- the TENGs used in external resistor matching and capacitor charging were assembled with a CNF film and an FEP film of 40 cm 2 active area.
- the thickness of the CNF was 70 ⁇ m, and the FEP 60 ⁇ m.
- the size of the substrate was 7.4 cm ⁇ 10 cm.
- a eff ⁇ ⁇ is constant for a given TENG.
- TENG as a capacitor is identical to three capacitors connected in series. So the capacitance of the TENG can be calculated according to the equation:
- C 1 1 C 1 + 1 C 2 + 1 C 3 , where C 1 , C 2 and C 3 are the capacitance of the corresponding air capacitor, CNF capacitor, and FEP capacitor.
- a eff-a 1 ⁇ 10 ⁇ 4 m 2
- a eff-b 9 ⁇ 10 ⁇ 4 m 2
- a eff-c 16 ⁇ 10 ⁇ 4 m 2
- a eff-d 25 ⁇ 10 ⁇ 4 m 2
- a eff-e 40 ⁇ 10 ⁇ 4 m 2
- the plotting of V vs. t for TENGs of different area was shown in FIG. 5B .
- the output energy E is 0.022mJ as shown above. Therefore, the ratio of input mechanical energy to output electrical energy was calculated to be:
- This example illustrates solution-phase methods for synthesizing positive and negative active layers comprising cellulose nanofibrils and methods for characterizing the performance of TENGs made therefrom.
- the surface charge densities of the unfunctionalized cellulose and the various functionalized celluloses studied are shown in Table 1.
- the surface charge densities for some conventional polymeric active layer materials are also provided.
- Methylcellulose One gram of CNFs was mercerized in 20 ml 50% NaOH solution for 1 h at room temperature ( ⁇ 23° C.). Then the cellulose was collected by centrifugation to remove the NaOH solution and washed with DI water for several times. The CNFs were added into 12 ml dimethyl sulfide solution (3 ml dimethyl sulfide in 9 ml acetone). After reaction for 2 hrs at room temperature, the system was washed with acetone and centrifuged repeatedly. The collected CNFs were dried at 60° C.
- Nitrocellulose To synthesize nitrocellulose, a nitration acid mixture was prepared by mixing 25 wt % HNO 3 , 59.5 wt % H 2 SO 4 , and 15.5 wt % H 2 O at room temperature. Dried CNFs were immersed in the acid at room temperature for 2 hrs under stirring. 50 ml of acid was used for each gram of cellulose. After the reaction, CNFs were retrieved by washing the reactants with DI water and centrifugation for several cycles. Then the CNFs were distributed in DI water and boiled twice for 1.5 hr each time. The CNFs were then washed twice using DI water containing 0.027% of sodium carbonate. After centrifugation and drying at 60° C., the nitrocellulose was distributed in ethyl acetate, and the nitrocellulose film was obtained after the volatilization of ethyl acetate in atmosphere at room temperature.
- KPM mapping revealed that untreated (pristine) cellulose had an average surface potential of ⁇ 360 mV; amine cellulose had a surface potential of ⁇ 420 mV; methylcellulose showed a very positive surface potential of ⁇ 2V; and nitrocellulose showed a surface potential of ⁇ 400 mV.
- the triboelectric output between different pairs of pristine and treated cellulose was measured based on the simple vertical contacting design. The outputs are shown in FIGS. 9A-9G . As expected, the output from a pair of pristine cellulose film was nearly negligible ( FIG. 9A ). The three chemically treated cellulose film all showed enhanced output in pair with the pristine cellulose film. Among them, Nitrocellulose exhibited the highest output ( FIG. 9B ), while the output from ethylcellulose and amine cellulose exhibited similar output, which was ⁇ 2 times smaller than that of the nitrocellulose ( FIGS. 9C and 9D ). When nitrocellulose was paired with methyl cellulose, the output was even doubled compared to the nitrocellulose-pristine cellulose pair ( FIG. 9E ). Similar significant output enhancement was also obtained from nitro-amine and methyl-amine pairs ( FIG. 9F and FIG. 9G ). The average peak voltages for the active layer pairs are listed in Table 2.
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Abstract
Description
By examining the testing protocols, it was hypothesized that the voltage-surface area relation was likely a result of the discharging behavior of TENGs in an RC circuit, where the resistance of the oscilloscope is not infinitely large. Since C is directly related to Aeff, a larger area TENG has a larger time constant τ=RC. Therefore, given that all TENGs have the same initial Voc, their V˜t relationships were calculated and plotted (detailed calculation is included in the Supplementary Materials provided below). As shown in
is constant for a given TENG.
and the voltage decreases following
where τ=RC.
where C1, C2 and C3 are the capacitance of the corresponding air capacitor, CNF capacitor, and FEP capacitor.
to C1, C2 and C3 in the above equation and you obtain:
The plotting of V vs. t for TENGs of different area was shown in
therefore, the energy output of the TENG fiberboard was calculated as:
TABLE 1 | |||
Surface charge q (pC) per | |||
~0.13 cm2 contact area after | |||
Type of Cellulose | contact with Au | ||
Amine cellulose | ca. +1.5 | ||
Ethylcellulose | +1.3 | ||
Methylcellulose | ca. +1.3 | ||
|
+1.2 | ||
Cellulose sulfate | ca. +1 | ||
Cellulose acetate | ca. +0.5 | ||
Cellulose | +0.15 | ||
Polyethylene terephthalate PET | −0.8 | ||
Nitrocellulose | ca. −1.6 | ||
Fluorocellulose | ca. −2.8 | ||
Polytetrafluoroethylene | −2.8 | ||
PTFE (Teflon) | |||
TABLE 2 | |||
Functionalization of | |||
Cellulose Pairs in | |||
TENG | Average Peak Voltage Output (Volt) | ||
Pristine + Pristine | 0.080 | ||
Nitro + Pristine | 0.632 | ||
Methyl + Pristine | 0.216 | ||
Amine + Pristine | 0.188 | ||
Methyl + Nitro | 1.102 | ||
Nitro + Amine | 0.667 | ||
Methyl + Amine | 0.376 | ||
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